View Compilation Error

0_0_20441363_22380.cpp: In function 'int main()':
0_0_20441363_22380.cpp:9:29: error: 'memset' was not declared in this scope
         memset(n,0,sizeof(n));  
                             ^
0_0_20441363_22380.cpp:10:27: error: 'strlen' was not declared in this scope
         int len=strlen(buf);  
                           ^